Food Science Commons^™

Aromatic Amino Acid Catabolism By Lactobacillus Spp.: Biochemistry And Contribution To Cheese Flavor Development, Sanjay Gummalla

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Amino acids derived from the degradation of casein in cheese serve as precursors for the generation of desirable and undesirable flavor compounds. Microbial degradation of aromatic amino acids is associated with the formation of aroma compounds that impart putrid-fecal, barny-utensil, and floral off-flavors in cheese, but pathways for their production had not been established. This study investigated Tyr and Phe catabolism by Lactobacillus casei and Lactobacillus helveticus cheese flavor adjuncts under simulated Cheddar cheese-ripening conditions (pH 5.2, 4% NaCl, 15°C, no sugar). Enzyme assays of cell-free extracts and micellar electrokinetic capillary chromatography of supernatants indicated that L. casei and L. …

The Effect Of Lactobacillus Helveticus And Propionibacterium Freudenreichii Ssp. Shermanii Combinations On Propensity For Split Defect In Swiss Cheese, Steven R. White

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

One of the least controlled defects in Swiss cheese is development of splits. Split defect is characterized by fissures or cracks in the body of the cheese that can be as short as 1 cm in length or long enough to span a 90-kg block. This defect appears during refrigerated storage after the cheese is removed from the warm room. Swiss cheese with splits is downgraded because it is unsuitable for use on high-speed slicing equipment (up to 1,000 slices per minute).

A 2x2x2 factorial experiment was used to determine the effect of different commercial Lactobacillus helveticus starters combined with …

Tryptophan Catabolism In Brevibacterium Linens Bl2, Madhavi Ummadi

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Recent studies suggest aromatic amino acid catabolism by starter lactococci and flavor adjunct bacteria have a significant impact on off-flavor development during Cheddar cheese ripening. We hypothesized that a flavor adjunct bacterium, Brevibacterium linens BL2, produces off-flavor compounds from aromatic amino acid metabolism that will have a detrimental impact on cheese flavor.

The mechanism of tryptophan (Trp) catabolism in Brevibacterium linens BL2, was investigated in a chemically defined medium during incubation in laboratory conditions (no carbohydrate, pH 6.50, 220 rpm, 25°C) and cheese-like conditions (no carbohydrate, 4% NaCl, static incubation, l5°C). In laboratory conditions, metabolic studies and enzyme assays confirmed …